Method and apparatus to process 4-operand simd integer multiply-accumulate instruction

ABSTRACT

According to one embodiment, a processor includes an instruction decoder to receive an instruction to process a multiply-accumulate operation, the instruction having a first operand, a second operand, a third operand, and a fourth operand. The first operand is to specify a first storage location to store an accumulated value; the second operand is to specify a second storage location to store a first value and a second value; and the third operand is to specify a third storage location to store a third value. The processor further includes an execution unit coupled to the instruction decoder to perform the multiply-accumulate operation to multiply the first value with the second value to generate a multiply result and to accumulate the multiply result and at least a portion of a third value to an accumulated value based on the fourth operand.

TECHNICAL FIELD

Embodiments of the present invention relate generally to instructionprocessing apparatuses. More particularly, embodiments of the inventionrelate to instruction processing apparatuses to process 4-operand SIMDinteger multiply-accumulate instructions.

BACKGROUND ART

Some operations, such as public key cryptographic operations andlong-integer arithmetic, require efficient multi-precisionmultiplication implementations. FIG. 1 depicts an example of amultiply-accumulate operation of a one data block multiplied by an eightdata block (1×8 multiply-accumulate). Conventional implementations usemodular exponentiation, which translates to performing a very largenumber of multi-precision multiplications and additions over multipleinstructions.

Previously disclosed is a multiply-accumulate instruction with threeoperands which produces a result twice the width of the operand and wastherefore defined to write to a pair of destination registers (for thelow and high part of the result). The previous 3-operandmultiply-accumulate instruction is defined as:

Hi_(n) :S _(n) =A _(i) *B _(n) +S _(n)

Each multiply operation generates 128 bits (64*64=128 bits) and eachmultiplication requires two additions (implying two independent carrychains):

S _(n) =S _(n)+Lo_(n)

S _(n) =S _(n)+Hi_(n-1)

The previous multiply-accumulate operation requires a first instructionto perform a multiplication and an addition, and a second instruction toperform a second addition. It would need 8 64*64 bit multipliers in adata-path, whose cost is substantial. There are substantial othermicro-operations (μops) that need to execute on the data-path. The μopsconsume precious 512-bit execution ports, limiting the ideal performancethat could be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are illustrated by way of example and notlimitation in the figures of the accompanying drawings in which likereferences indicate similar elements.

FIG. 1 depicts details of the integer multiply-accumulate operation.

FIG. 2 is a block diagram of an execution pipeline of a processor orprocessor core according to one embodiment of the invention.

FIG. 3 depicts details of the operands of a 4-operand SIMD integermultiply-accumulate instruction according to one embodiment.

FIG. 4 is a block diagram illustrating a 4-operand SIMD integermultiply-accumulate instruction according to one embodiment.

FIG. 5 is pseudocode illustrating a process of a 4-operand SIMD integermultiply-accumulate instruction according to one embodiment.

FIG. 6 is pseudocode illustrating a process of a call to a 4-operandSIMD integer multiply-accumulate instruction according to oneembodiment.

FIG. 7A illustrates an exemplary advanced vector extensions (AVX)instruction format according to one embodiment of the invention.

FIG. 7B illustrates an exemplary advanced vector extensions (AVX)instruction format according to another embodiment of the invention.

FIG. 7C illustrates an exemplary advanced vector extensions (AVX)instruction format according to another embodiment of the invention.

FIG. 8A is a block diagram illustrating a generic vector friendlyinstruction format and class A instruction templates thereof accordingto embodiments of the invention.

FIG. 8B is a block diagram illustrating the generic vector friendlyinstruction format and class B instruction templates thereof accordingto embodiments of the invention.

FIG. 9A is a block diagram illustrating an exemplary specific vectorfriendly instruction format according to one embodiment of theinvention.

FIG. 9B is a block diagram illustrating a generic vector friendlyinstruction format according to another embodiment of the invention.

FIG. 9C is a block diagram illustrating a generic vector friendlyinstruction format according to another embodiment of the invention.

FIG. 9D is a block diagram illustrating a generic vector friendlyinstruction format according to another embodiment of the invention.

FIG. 10 is a block diagram of register architecture according to oneembodiment of the invention.

FIG. 11A is a block diagram illustrating both an exemplary in-orderpipeline and an exemplary register renaming, out-of-orderissue/execution pipeline according to embodiments of the invention.

FIG. 11B is a block diagram illustrating both an exemplary embodiment ofan in-order architecture core and an exemplary register renaming,out-of-order issue/execution architecture core to be included in aprocessor according to embodiments of the invention.

FIG. 12A is a block diagram of a processor core according to oneembodiment of the invention.

FIG. 12B is a block diagram of a processor core according to anotherembodiment of the invention.

FIG. 13 is a block diagram of a processor according to embodiments ofthe invention.

FIG. 14 is a block diagram of a system in accordance with one embodimentof the invention.

FIG. 15 is a block diagram of a more specific exemplary system inaccordance with an embodiment of the invention.

FIG. 16 is a block diagram of a more specific exemplary system inaccordance with another embodiment of the invention.

FIG. 17 is a block diagram of a SoC in accordance with an embodiment ofthe invention.

FIG. 18 is a block diagram contrasting the use of a software instructionconverter to convert binary instructions in a source instruction set tobinary instructions in a target instruction set according to embodimentsof the invention.

DESCRIPTION OF THE EMBODIMENTS

Various embodiments and aspects of the invention will be described withreference to details discussed below, and accompanying drawings willillustrate the various embodiments. The following description anddrawings are illustrative of the invention and are not to be construedas limiting the invention. Numerous specific details are described toprovide a thorough understanding of various embodiments of the presentinvention. However, in certain instances, well-known or conventionaldetails are not described in order to provide a concise discussion ofembodiments of the present invention.

Reference in the specification to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin conjunction with the embodiment can be included in at least oneembodiment of the invention. The appearances of the phrase “in oneembodiment” in various places in the specification do not necessarilyall refer to the same embodiment.

According to some embodiments, a new instruction set architecture (ISA)is utilized to perform one or more multiply-accumulate operations inresponse to a single instruction (e.g., single instruction multiple dataor SIMD instruction) to in order to improve the speed and efficiency ofthe multiply-accumulate operation. A conventional system has to utilizemultiple instructions to perform a multiply-accumulate operation. Theperformance may be improved by reducing the number of instructionsrequired to perform a multiply-accumulate operation to a singleinstruction. In one embodiment, three registers consisting of at least512 bits and one register consisting of at least 8 bits are used tostore four operands, such that at least four multiply-accumulateoperations, each using 128 bits of the first three operands and 1 bit ofthe fourth operand, may be performed by a processor such as a vectorcapable processor in response to a single instruction.

FIG. 2 is a block diagram of an execution pipeline of a processor orprocessor core according to one embodiment of the invention. Referringto FIG. 2, processor 200 may represent any kind of instructionprocessing apparatuses. For example, processor 200 may be ageneral-purpose processor. Processor 200 may be any of various complexinstruction set computing (CISC) processors, various reduced instructionset computing (RISC) processors, various very long instruction word(VLIW) processors, various hybrids thereof, or other types of processorsentirely. Processor 200 may also represent one or more processor cores.

Processor cores may be implemented in different ways, for differentpurposes, and in different processors. For instance, implementations ofsuch cores may include: 1) a general purpose in-order core intended forgeneral-purpose computing; 2) a high performance general purposeout-of-order core intended for general-purpose computing; 3) a specialpurpose core intended primarily for graphics and/or scientific(throughput) computing. Implementations of different processors mayinclude: 1) a central processing unit (CPU) including one or moregeneral purpose in-order cores intended for general-purpose computingand/or one or more general purpose out-of-order cores intended forgeneral-purpose computing; and 2) a coprocessor including one or morespecial purpose cores intended primarily for graphics and/or scientific(throughput). Such different processors lead to different computersystem architectures, which may include: 1) the coprocessor on aseparate chip from the CPU; 2) the coprocessor on a separate die in thesame package as a CPU; 3) the coprocessor on the same die as a CPU (inwhich case, such a coprocessor is sometimes referred to as specialpurpose logic, such as integrated graphics and/or scientific(throughput) logic, or as special purpose cores); and 4) a system on achip that may include on the same die the described CPU (sometimesreferred to as the application core(s) or application processor(s)), theabove described coprocessor, and additional functionality. Exemplarycore architectures are described next, followed by descriptions ofexemplary processors and computer architectures.

In one embodiment, processor 200 includes, but is not limited to,instruction decoder 202 and one or more execution units 203. Instructiondecoder 202 is to receive and decode instructions 201 from aninstruction fetch unit (not shown). Instruction decoder 202 may generateand output one or more micro-operations, micro-code, entry points,microinstructions, other instructions, or other control signals, whichreflect, or are derived from, the instructions. Instruction decoder 202may be implemented using various different mechanisms. Examples ofsuitable mechanisms include, but are not limited to, microcode read onlymemories (ROMs), look-up tables, hardware implementations, programmablelogic arrays (PLAs), and the like.

Execution units 203, which may include an arithmetic logic unit, oranother type of logic unit capable of performing operations based oninstructions. As a result of instruction decoder 202 decoding theinstructions, execution unit 203 may receive one or moremicro-operations, micro-code entry points, microinstructions, otherinstructions, or other control signals, which reflect, or are derivedfrom, the instructions. Execution unit 203 may be operable as a resultof instructions indicating one or more source operands (SRC) and tostore a result in one or more destination operands (DEST) of a registerset indicated by the instructions. Execution unit 203 may includecircuitry or other execution logic (e.g., software combined withhardware and/or firmware) operable to execute instructions or othercontrol signals derived from the instructions and perform an operationaccordingly. Execution unit 203 may represent many kinds of executionunits such as logic units, arithmetic logic units (ALUs), arithmeticunits, integer units, etc.

Some or all of the source and destination operands may be stored in avariety of storage locations such as registers of a register set,memory, or a combination thereof. The register set may be part of aregister file, along with potentially other registers, such as statusregisters, flag registers, etc. A register may be a storage location ordevice that may be used to store data. The register set may often bephysically located on a die with the execution unit(s). The registersmay be visible from the outside of the processor or from a programmer'sperspective. For example, instructions may specify operands stored inthe registers. Various different types of registers are suitable, aslong as they are capable of storing and providing data as describedherein. The registers may or may not be renamed. Examples of suitableregisters include, but are not limited to, dedicated physical registers,dynamically allocated physical registers using register renaming,combinations of dedicated and dynamically allocated physical registers,etc. Alternatively, one or more of the source and destination operandsmay be stored in a storage location other than a register, such as, forexample, a location in system memory.

Referring back to FIG. 2, according to one embodiment, execution unit203 includes one or more Multiply-Accumulate units 204 to perform, inresponse to an received and provided by instruction decoder 202, one ormore multiply-accumulate operations using data 206. The one or moremultiply-accumulate operations are performed in response to a singleinstruction as a single instruction multiple data (SIMD) instruction.The number of multiply-accumulate operations depends on the specificdesign or configuration (e.g., pipeline latency requirement) of theprocessor pipeline, which may be configured to an appropriate numberthat will optimize the overall performance of the processor pipeline.For the purpose of illustration, it is assumed four multiply-accumulateoperations are performed in a single SIMD cycle. It will be appreciated,more or fewer multiply-accumulate operations can also be performed in asingle SIMD cycle, as long as the required resources such as registersor memory with proper sizes are available.

According to one embodiment, one or more multiply-accumulate operationsare performed in response to a single instruction as a singleinstruction multiple data (SIMD) instruction. In one embodiment, themultiply-accumulate instruction may be defined as:

-   -   vpmac4Q (zmm dst, zmm src1, zmm src2, byte imm8);

Instead of requiring multiple instructions to perform themultiply-accumulate operation, the invention allows for themultiply-accumulate operation to be performed in a single instruction.This operation may be represented as:

(a*b)+c+d

In one embodiment, the first operand represents a source/destinationregister to store a current vpmac4Q accumulated value as an input and anext vpmac4Q accumulated value as an output representing a result of amultiply-accumulate operation. The second and third operands representregisters/memory to store data utilized in the multiply-accumulateoperation. The fourth operand represents a register/memory to store dataused to determine which portion of the third operand to utilize in themultiply-accumulate operation. As explained below, after themultiply-accumulate operation is complete, the value resulting from themultiplication and two additions is stored in the register/memoryrepresented by the first operand and the carry bits resulting from theadditions are stored in a second portion of the register represented bythe first operand.

In one embodiment, the registers involved have at least 512 bits tostore the source/destination data, the data used in the multiplicationand addition, and at least 8 bits to store the data used to determinewhich portion the other registers will be used. In such an embodiment,the first three operands may represent registers referred to as ZMMregisters, representing a 512-bit register. It should be noted thatsmaller or larger registers may be used as long as the size of theoperands or number of iterations performed is adjusted accordingly.Throughout this application, multiply-accumulate operations using threeoperands representing 512-bit registers and one operand representing an8-bit register are described for the purpose of illustration; however,other size registers and operands may also be applied. Also through thisapplication, the term register will be used to refer to the numeroustypes of storage locations available for storing data including, but notlimited to, dedicated physical registers, dynamically allocated physicalregisters using a register renaming mechanism (e.g., the use of aRegister Alias Table (RAT), system memory, and memory located on anexternal device.

In one embodiment, the use of a ZMM operand corresponds to a 512-bitregister. This can be preceded by two similar operands, an XMM operandwhich corresponds to a 128-bit register and a YMM register whichcorresponds to a 256-bit register. FIG. 3 depicts one embodiment of fourregisters that are represented by the four operands which are utilizedin the current invention. In one embodiment, the multiply-accumulateinstruction includes multiple lanes of operations, which can beperformed by a processor in parallel or in a pipelined manner. Each laneuses a different portion of each operand.

Referring to FIG. 3, in this example, storage location 300 depicts theregister represented by the first operand, ZMM dst. In one embodiment,the first iteration (e.g., lane) of the instruction utilizes the upperportion of the first 128 bits depicted by storage location 307. In asecond embodiment, the lower portion may be utilized.

Storage location 309 depicts the register represented by the secondoperand, ZMM src1. The first iteration of the instruction utilizes thefirst 128 bits of storage location 309 corresponding to storagelocations 316 and 317. Storage locations 316 and 317 represent the twovalues to be multiplied, a₀ and b₀ respectively.

According to some embodiments, storage location 318 depicts the registerrepresented by the third operand, ZMM src2. The first iteration of theinstruction utilizes either the upper or lower portion of the first 128bits of storage location 318, represented by storage locations 325 and326 respectively. The fourth operand is used to determine which portionof the first 128 bits, for example, upper or lower, will be used.Storage location 327 depicts the register represented by the fourthoperand. In one embodiment, the first bit of the byte-sized storagelocation is utilized in the first iteration. In FIG. 3, storage location335 is equal to zero which may represent that the lower portion of thefirst 128 bits of storage location 318 will be utilized (storagelocation 326).

When the first iteration of the multiply-accumulate operation isfinished, in one embodiment, the result is stored in the lower portionof the first 128 bits of the register represented by the first operand,represented by storage location 308. The carry bits resulting from themultiply-accumulate operation are stored in the upper portion of thefirst 128 bits of the register represented by the first operand,represented by storage location 307. In one embodiment, the instructionthen performs a second iteration such that a counter has beenincremented by 128 to shift to the second block of 128 bits of theregisters represented by the first three operands. Referring to FIG. 3,this may be represented by storage locations 305 and 306 for the firstoperand, storage locations 314 and 315 for the second operand, andstorage locations 323 and 324 for the third operand.

In one embodiment, the entire multiply-accumulate instruction may becompleted in a single clock cycle. This may be accomplished by way ofparallel processing; each processor core performs one iteration or laneconsisting of 128 bits of each register represented by the first threeoperands. In such an embodiment, where four processor cores areavailable, the first processor core may perform the multiply-accumulateoperation using the first 128 bits of the register represented by thefirst operand, represented by storage locations 307 and 308. Similarly,the first processor core may use the first 128 bits of the registerrepresenting the second operand, represented by storage locations 316and 317, and the first processor core may use the first 128 bits of theregister represented by the third operand, represented by storagelocations 325 and 326. The first processor core may use the first bit ofthe fourth operand, represented by storage location 331. In such anembodiment, the second processor core may perform themultiply-accumulate operation using the second 128 bits of the registersrepresented by the first three operands and the second bit of the fourthoperand (represented by storage locations 305/306, 314/315, 323/324, and334 respectively). Similarly, the third processor core would utilize thethird 128 bits of the registers represented by the first three operandsand the third bit of the fourth operand (represented by 303/304,312/313, 321/322, and 333 respectively). The fourth processor core mayperform the multiply-accumulate operation on the fourth 128 bits of theregisters represented by the first three operands and the fourth bit ofthe fourth operand (represented by storage locations 301/302, 310/311,319/320, and 332 respectively).

Referring to FIG. 4, method 400 illustrates one embodiment of a flowdiagram of executing a multiply-accumulate instruction. The method ofexecuting the instruction is initiated when an instruction decoder (202)receives the multiply-accumulate instruction as a single instructionhaving at least four operands, represented by block 410. In oneembodiment, the instruction may take the form:

-   -   vpmac4Q (zmm dst, zmm src1, zmm src2, byte imm8);

The following illustration provides an example of one embodiment and isnot meant to limit the breadth of the order of which the operands arepassed, where in the registers certain data is stored, or other similarcharacteristics. Once the instruction has been received, an executionunit (203) coupled to the instruction decoder (202), in response to theinstruction, performs a multiplication between a first portion (e.g., alower portion) of the second operand, (e.g., ‘b’ derived from ZMM src1)and a second portion (e.g., an upper portion) of the second operand,(e.g., ‘a’ derived from ZMM src1). In one embodiment, the values to bemultiplied (e.g., ‘a’ and ‘b’) are initially concatenated and stored inthe register represented by the second operand. For instance, ‘a’ and‘b’ may represent two 64-bit integers. They may be concatenated into a128-bit integer and the pointer to the first bit of the 128 bits will bepassed as an operand into the instruction. This is represented by block420.

Upon completion of the multiplication, block 420, the execution unitthen performs an addition between the product of the multiplicationbetween ‘a’ and ‘b’ and a portion of the third operand (e.g., ‘c’derived from ZMM src2) based on the value of the fourth operand (e.g.,byte imm8). The fourth operand may represent a value, (e.g., logicalvalue of ‘0’ or ‘1’) which indicates whether a first portion or secondportion (e.g., the upper or lower portion) of the third operand will beused in the addition. By way of example, the fourth operand may be equalto logical value ‘0’ representing that the first portion (e.g., thelower portion) of the third operand will be utilized. This isrepresented by block 430.

A second addition is then performed by the execution unit (203),represented by block 440, between the sum of the first addition and aportion of the first operand (e.g., ‘d’ derived from ZMM dst). In oneembodiment, the instruction may indicate that the second portion (e.g.,the upper portion) of the first operand be used in the second addition.In this instance, d(i+127:i+64) would be utilized, where i represents acurrent iteration. According to one embodiment, ZMM dst may represent a512-bit register and where i=0 and the instruction indicates that theupper portion of ‘d’ will be utilized in the second addition, d(127:64)will be used. The final value of the multiply-accumulate instructionwill then be stored in a storage location associated with the firstoperand, block 450. A portion of the final value of themultiply-accumulate instruction may be used as an operand in a latercall to the instruction. In one embodiment, the final value is stored inthe register represented by the first operand and either the upper orlower portion of the appropriate 128-bit segment will be utilized. Forexample, upon the second call to the instruction, where the instructionindicates that the upper portion of the register represented by thefirst operand is to be used, dst(127:64) will be used. In thissituation, dst(127:64) represents the upper portion of the final valueof the previous call to the instruction.

FIG. 5 is pseudocode illustrating a process of the invention accordingto one embodiment. Line 2, a for loop, is the starting point of thepseudocode. The for loop is intended in this embodiment to illustratethat the instruction will perform multiple (e.g., four) lanes of themultiply-accumulate operation in a single instruction. The operands ZMMdst, ZMM src1, and ZMM src2, in this embodiment, represent three 512-bitregisters. Each iteration through the for loop will perform themultiply-accumulate operation on a 128-bit portion of each of the threeoperands listed above. The counter i represents the current iterationthrough the 512-bit registers as the counter is incremented by 128 aftereach operation has been performed.

Lines 3-5 show three operands being initialized with the values in theregisters represented by the first three operands. For example, ifexecution unit 203 is performing the first iteration of the instruction,i will be equal to zero. In that case, one operand, e.g., SRC1 will beinitialized with the first 128 bits of the ZMM src1 (storage locations316 and 317). Likewise, SRC2 will be initialized with the first 128 bitsof the ZMM src2 (storage locations 325 and 326) and SRC3 will beinitialized with the first 128 bits of the ZMM dst (storage locations307 and 308).

Line 6 stores the lower portion of SRC1, SRC1(63:0), into register rax.Line 7 stores the upper portion of SRC1, SRC1(127:64), into registerrdx. Line 8 performs the multiplication of the multiply-accumulateoperation between the values in registers rax and rdx and stores theproduct in register rax.

According to the embodiment illustrated in FIG. 5, line 9 stores thelower or upper portion of SRC2, SRC2(63:0) or SRC2(127:64) in registerr9 based on the value of the fourth operand, imm8. FIG. 5 demonstratesdetermining which portion of SRC2 to use based on the value in the0^(th) bit of the register represented by the fourth operand. Line 10stores the upper portion of SRC3 in r10.

Line 11 performs the addition between the product of the multiplication,the value stored in register rax and the value stored in register r9 andstores the sum in register rax. Line 12 performs an addition between thecarry bits that resulted from the addition in line 11 and the valuecurrently in register rdx and stores the result in rdx. Line 13 performsthe addition between the value currently in register rax and the valuein register r10 stores the value in register rax. Line 14 performs anaddition between the carry bits that resulted from the addition in line13 and the value currently in register rdx and stores the sum inregister rdx.

Line 15 moves the value in register rax into the register represented byoperand ZMM dst. According to one embodiment, register rax stores a64-bit integer resulting from the multiply-accumulate operation. Thisvalue is stored in the lower portion of the operand ZMM dst. Line 16moves the value in register rdx into the register represented by operandZMM dst. According to one embodiment, the value in register rdx is movedinto the upper portion of the register represented by operand ZMM dst.

The instruction then loops back to line 2 and increments the counter iby 128. The instruction determines whether i is equal to 512 signalingthat the instruction has gone through four cycles of themultiply-accumulate operation and will return from the instruction inthat instance. If the counter i is less than 512 bits, another iterationof the multiply-accumulate instruction will be performed in the samemanner as described above.

In another embodiment, the instruction may be implemented on a processorwith multiple processor cores, for example. In such an embodiment, thefour iterations of the instruction may be run simultaneously, each on aseparate processor core. Note that the operations as shown in FIG. 5 aredescribed for illustrative purposes only. Other implementations may alsobe utilized.

FIG. 6 is pseudocode illustrating a process for a 1*8 64-bit Qword callto the multiply-accumulate instruction according to one embodiment. AQword represents a unit of data that has a length of 64 bits. Line 1initializes the lower portion of register T1 with the value in A_(i).According to one embodiment, A, is a 64-bit integer. Line 2 shifts thevalue in the lower portion of T1 to the upper portion of T1. In theembodiment illustrated by FIG. 6, A, is a 64-bit integer and is shifted64 bits (shown as 8 bytes). Line 3 initializes register T2 with a valueof 0. In one embodiment, T2 may represent the destination register inwhich the result of the multiply-accumulate instruction will be stored.

Line 4 moves the value in B_(o) into the lower portion of T1 andmaintains the value from A, in the upper portion. According to theembodiment shown in FIG. 6, T1 would resemble the following after lines1-4 have executed:

The above illustrates that B₀ is being stored in the lower portion ofthe register, or bits 63:0 and A_(i) is being stored in the upperportion of the register, or bits 127:64.

Line 5 is the call to the multiply-accumulate instruction, shown in oneembodiment in FIG. 5. In the embodiment shown in FIG. 6, T2 in the firstoperand passed to the multiply-accumulate instruction. This will serveas the destination register for the result of the multiply-accumulateinstruction. This register may also serve as an operand for future callsto the instruction allowing that call to utilize previousmultiply-accumulate results within the instruction. Line 6 moves theresult from the call to the multiply-accumulate instruction, which isstored in register T2, in register DST.

Line 7 begins to repeat the process of initializing operand T1,executing a call to the multiply-accumulate instruction and storing theresult in a register. Line 7 initializes T1 with the value in B₁. Line 8executes a call to the multiply-accumulate instruction and line 9 loadsthe result of the call to the multiply-accumulate instruction from line8 into register S₀. Lines 10-27 repeat this process, each timeinitializing T1 with a new value and storing the result from the call tothe multiply-accumulate instruction in a new register.

According to some embodiments, a processor includes an instructiondecoder to receive an instruction to process a multiply-accumulateoperation, the instruction having a first operand, a second operand, athird operand, and a fourth operand; and an execution unit coupled tothe instruction decoder to perform the multiply-accumulate operation onthe first operand, the second operand, and at least a portion of thethird operand as determined by the fourth operand. The first operandspecifies a first storage location to store an accumulated value. Thesecond operand specifies a second storage location to store a firstvalue and a second value, where the execution unit is to multiple thefirst value and the second value to generate a multiply result and toaccumulate the multiply result to the accumulated value. The thirdoperand specifies a third storage location to store a third value to beadded to the accumulated value. The fourth operand specifies a fourthstorage location to store a value indicating at least a portion of thethird value to be added to the accumulated value. The first, second, andthird operands have at least 512 bits and the execution unit is toperform at least four iterations of the multiply-accumulate operation,each iteration occupying at least 128 bits. For a current iteration ofmultiply-accumulate operations, a multiplication is performed betweenthe (i+63:i) bits of the second operand and the (i+127:i+64) bits of thesecond operand, a first addition is performed between the multiplicationand the (i+63:i) bits of the first operand, and a second addition isperformed between the first addition and the (i+63:i) bits of the thirdoperand as specified by the fourth operand. A third addition isperformed between a first set of carry bits resulting from the firstaddition and a second set of carry bits resulting from the secondaddition. The second addition is performed between the first additionand the (i+127:i+64) bits of the third operand as specified by thefourth operand.

An instruction set, or instruction set architecture (ISA), is the partof the computer architecture related to programming, and may include thenative data types, instructions, register architecture, addressingmodes, memory architecture, interrupt and exception handling, andexternal input and output (I/O). The term instruction generally refersherein to macroinstructions—that is instructions that are provided tothe processor (or instruction converter that translates (e.g., usingstatic binary translation, dynamic binary translation including dynamiccompilation), morphs, emulates, or otherwise converts an instruction toone or more other instructions to be processed by the processor) forexecution—as opposed to micro-instructions or micro-operations(micro-ops)—that is the result of a processor's decoder decodingmacroinstructions.

The ISA is distinguished from the microarchitecture, which is theinternal design of the processor implementing the instruction set.Processors with different microarchitectures can share a commoninstruction set. For example, Intel® Pentium 4 processors, Intel® Core™processors, and processors from Advanced Micro Devices, Inc. ofSunnyvale Calif. implement nearly identical versions of the x86instruction set (with some extensions that have been added with newerversions), but have different internal designs. For example, the sameregister architecture of the ISA may be implemented in different ways indifferent microarchitectures using well-known techniques, includingdedicated physical registers, one or more dynamically allocated physicalregisters using a register renaming mechanism (e.g., the use of aRegister Alias Table (RAT), a Reorder Buffer (ROB), and a retirementregister file; the use of multiple maps and a pool of registers), etc.Unless otherwise specified, the phrases register architecture, registerfile, and register are used herein to refer to that which is visible tothe software/programmer and the manner in which instructions specifyregisters. Where a specificity is desired, the adjective logical,architectural, or software visible will be used to indicateregisters/files in the register architecture, while different adjectiveswill be used to designation registers in a given microarchitecture(e.g., physical register, reorder buffer, retirement register, registerpool).

An instruction set includes one or more instruction formats. A giveninstruction format defines various fields (number of bits, location ofbits) to specify, among other things, the operation to be performed(opcode) and the operand(s) on which that operation is to be performed.Some instruction formats are further broken down though the definitionof instruction templates (or subformats). For example, the instructiontemplates of a given instruction format may be defined to have differentsubsets of the instruction format's fields (the included fields aretypically in the same order, but at least some have different bitpositions because there are less fields included) and/or defined to havea given field interpreted differently. Thus, each instruction of an ISAis expressed using a given instruction format (and, if defined, in agiven one of the instruction templates of that instruction format) andincludes fields for specifying the operation and the operands. Forexample, an exemplary ADD instruction has a specific opcode and aninstruction format that includes an opcode field to specify that opcodeand operand fields to select operands (source 1/destination andsource2); and an occurrence of this ADD instruction in an instructionstream will have specific contents in the operand fields that selectspecific operands.

Scientific, financial, auto-vectorized general purpose, RMS(recognition, mining, and synthesis), and visual and multimediaapplications (e.g., 2D/3D graphics, image processing, videocompression/decompression, voice recognition algorithms and audiomanipulation) often require the same operation to be performed on alarge number of data items (referred to as “data parallelism”). SingleInstruction Multiple Data (SIMD) refers to a type of instruction thatcauses a processor to perform an operation on multiple data items. SIMDtechnology is especially suited to processors that can logically dividethe bits in a register into a number of fixed-sized data elements, eachof which represents a separate value. For example, the bits in a 256-bitregister may be specified as a source operand to be operated on as fourseparate 64-bit packed data elements (quad-word (Q) size data elements),eight separate 32-bit packed data elements (double word (D) size dataelements), sixteen separate 16-bit packed data elements (word (W) sizedata elements), or thirty-two separate 8-bit data elements (byte (B)size data elements). This type of data is referred to as packed datatype or vector data type, and operands of this data type are referred toas packed data operands or vector operands. In other words, a packeddata item or vector refers to a sequence of packed data elements, and apacked data operand or a vector operand is a source or destinationoperand of a SIMD instruction (also known as a packed data instructionor a vector instruction).

By way of example, one type of SIMD instruction specifies a singlevector operation to be performed on two source vector operands in avertical fashion to generate a destination vector operand (also referredto as a result vector operand) of the same size, with the same number ofdata elements, and in the same data element order. The data elements inthe source vector operands are referred to as source data elements,while the data elements in the destination vector operand are referredto a destination or result data elements. These source vector operandsare of the same size and contain data elements of the same width, andthus they contain the same number of data elements. The source dataelements in the same bit positions in the two source vector operandsform pairs of data elements (also referred to as corresponding dataelements; that is, the data element in data element position 0 of eachsource operand correspond, the data element in data element position 1of each source operand correspond, and so on). The operation specifiedby that SIMD instruction is performed separately on each of these pairsof source data elements to generate a matching number of result dataelements, and thus each pair of source data elements has a correspondingresult data element. Since the operation is vertical and since theresult vector operand is the same size, has the same number of dataelements, and the result data elements are stored in the same dataelement order as the source vector operands, the result data elementsare in the same bit positions of the result vector operand as theircorresponding pair of source data elements in the source vectoroperands. In addition to this exemplary type of SIMD instruction, thereare a variety of other types of SIMD instructions (e.g., that has onlyone or has more than two source vector operands, that operate in ahorizontal fashion, that generates a result vector operand that is of adifferent size, that has a different size data elements, and/or that hasa different data element order). It should be understood that the termdestination vector operand (or destination operand) is defined as thedirect result of performing the operation specified by an instruction,including the storage of that destination operand at a location (be it aregister or at a memory address specified by that instruction) so thatit may be accessed as a source operand by another instruction (byspecification of that same location by the another instruction).

The SIMD technology, such as that employed by the Intel® Core™processors having an instruction set including x86, MMX™, Streaming SIMDExtensions (SSE), SSE2, SSE3, SSE4.1, and SSE4.2 instructions, hasenabled a significant improvement in application performance. Anadditional set of SIMD extensions, referred to the Advanced VectorExtensions (AVX) (AVX1 and AVX2) and using the Vector Extensions (VEX)coding scheme, has been, has been released and/or published (e.g., seeIntel® 64 and IA-32 Architectures Software Developers Manual, October2011; and see Intel® Advanced Vector Extensions Programming Reference,June 2011).

Embodiments of the instruction(s) described herein may be embodied indifferent formats. Additionally, exemplary systems, architectures, andpipelines are detailed below. Embodiments of the instruction(s) may beexecuted on such systems, architectures, and pipelines, but are notlimited to those detailed.

VEX encoding allows instructions to have more than two operands, andallows SIMD vector registers to be longer than 128 bits. The use of aVEX prefix provides for three-operand (or more) syntax. For example,previous two-operand instructions performed operations such as A=A+B,which overwrites a source operand. The use of a VEX prefix enablesoperands to perform nondestructive operations such as A=B+C.

FIG. 7A illustrates an exemplary AVX instruction format including a VEXprefix 2102, real opcode field 2130, Mod R/M byte 2140, SIB byte 2150,displacement field 2162, and IMM8 2172. FIG. 7B illustrates which fieldsfrom FIG. 7A make up a full opcode field 2174 and a base operation field2142. FIG. 7C illustrates which fields from FIG. 7A make up a registerindex field 2144.

VEX Prefix (Bytes 0-2) 2102 is encoded in a three-byte form. The firstbyte is the Format Field 2140 (VEX Byte 0, bits [7:0]), which containsan explicit C4 byte value (the unique value used for distinguishing theC4 instruction format). The second-third bytes (VEX Bytes 1-2) include anumber of bit fields providing specific capability. Specifically, REXfield 2105 (VEX Byte 1, bits [7-5]) consists of a VEX.R bit field (VEXByte 1, bit [7]-R), VEX.X bit field (VEX byte 1, bit [6]-X), and VEX.Bbit field (VEX byte 1, bit[5]-B). Other fields of the instructionsencode the lower three bits of the register indexes as is known in theart (rrr, xxx, and bbb), so that Rrrr, Xxxx, and Bbbb may be formed byadding VEX.R, VEX.X, and VEX.B. Opcode map field 2115 (VEX byte 1, bits[4:0]-mmmmm) includes content to encode an implied leading opcode byte.W Field 2164 (VEX byte 2, bit [7]-W)—is represented by the notationVEX.W, and provides different functions depending on the instruction.The role of VEX.vvvv 2120 (VEX Byte 2, bits [6:3]-vvvv) may include thefollowing: 1) VEX.vvvv encodes the first source register operand,specified in inverted (1s complement) form and is valid for instructionswith 2 or more source operands; 2) VEX.vvvv encodes the destinationregister operand, specified in is complement form for certain vectorshifts; or 3) VEX.vvvv does not encode any operand, the field isreserved and should contain 1111b. If VEX.L 2168 Size field (VEX byte 2,bit [2]-L)=0, it indicates 128 bit vector; if VEX.L=1, it indicates 256bit vector. Prefix encoding field 2125 (VEX byte 2, bits [1:0]-pp)provides additional bits for the base operation field.

Real Opcode Field 2130 (Byte 3) is also known as the opcode byte. Partof the opcode is specified in this field. MOD R/M Field 2140 (Byte 4)includes MOD field 2142 (bits [7-6]), Reg field 2144 (bits [5-3]), andR/M field 2146 (bits [2-0]). The role of Reg field 2144 may include thefollowing: encoding either the destination register operand or a sourceregister operand (the rrr of Rrrr), or be treated as an opcode extensionand not used to encode any instruction operand. The role of R/M field2146 may include the following: encoding the instruction operand thatreferences a memory address, or encoding either the destination registeroperand or a source register operand.

Scale, Index, Base (SIB)—The content of Scale field 2150 (Byte 5)includes SS 2152 (bits [7-6]), which is used for memory addressgeneration. The contents of SIB.xxx 2154 (bits [5-3]) and SIB.bbb 2156(bits [2-0]) have been previously referred to with regard to theregister indexes Xxxx and Bbbb. The Displacement Field 2162 and theimmediate field (IMM8) 2172 contain address data.

A vector friendly instruction format is an instruction format that issuited for vector instructions (e.g., there are certain fields specificto vector operations). While embodiments are described in which bothvector and scalar operations are supported through the vector friendlyinstruction format, alternative embodiments use only vector operationsthe vector friendly instruction format.

FIG. 8A, FIG. 8B, and FIG. 8C are block diagrams illustrating a genericvector friendly instruction format and instruction templates thereofaccording to embodiments of the invention. FIG. 8A is a block diagramillustrating a generic vector friendly instruction format and class Ainstruction templates thereof according to embodiments of the invention;while FIG. 8B is a block diagram illustrating the generic vectorfriendly instruction format and class B instruction templates thereofaccording to embodiments of the invention. Specifically, a genericvector friendly instruction format 2200 for which are defined class Aand class B instruction templates, both of which include no memoryaccess 2205 instruction templates and memory access 2220 instructiontemplates. The term generic in the context of the vector friendlyinstruction format refers to the instruction format not being tied toany specific instruction set.

While embodiments of the invention will be described in which the vectorfriendly instruction format supports the following: a 64 byte vectoroperand length (or size) with 32 bit (4 byte) or 64 bit (8 byte) dataelement widths (or sizes) (and thus, a 64 byte vector consists of either16 doubleword-size elements or alternatively, 8 quadword-size elements);a 64 byte vector operand length (or size) with 16 bit (2 byte) or 8 bit(1 byte) data element widths (or sizes); a 32 byte vector operand length(or size) with 32 bit (4 byte), 64 bit (8 byte), 16 bit (2 byte), or 8bit (1 byte) data element widths (or sizes); and a 16 byte vectoroperand length (or size) with 32 bit (4 byte), 64 bit (8 byte), 16 bit(2 byte), or 8 bit (1 byte) data element widths (or sizes); alternativeembodiments may support more, less and/or different vector operand sizes(e.g., 256 byte vector operands) with more, less, or different dataelement widths (e.g., 128 bit (16 byte) data element widths).

The class A instruction templates in FIG. 8A include: 1) within the nomemory access 2205 instruction templates there is shown a no memoryaccess, full round control type operation 2210 instruction template anda no memory access, data transform type operation 2215 instructiontemplate; and 2) within the memory access 2220 instruction templatesthere is shown a memory access, temporal 2225 instruction template and amemory access, non-temporal 2230 instruction template. The class Binstruction templates in FIG. 8B include: 1) within the no memory access2205 instruction templates there is shown a no memory access, write maskcontrol, partial round control type operation 2212 instruction templateand a no memory access, write mask control, vsize type operation 2217instruction template; and 2) within the memory access 2220 instructiontemplates there is shown a memory access, write mask control 2227instruction template.

The generic vector friendly instruction format 2200 includes thefollowing fields listed below in the order illustrated in FIG. 8A andFIG. 8B. Format field 2240—a specific value (an instruction formatidentifier value) in this field uniquely identifies the vector friendlyinstruction format, and thus occurrences of instructions in the vectorfriendly instruction format in instruction streams. As such, this fieldis optional in the sense that it is not needed for an instruction setthat has only the generic vector friendly instruction format. Baseoperation field 2242—its content distinguishes different baseoperations.

Register index field 2244—its content, directly or through addressgeneration, specifies the locations of the source and destinationoperands, be they in registers or in memory. These include a sufficientnumber of bits to select N registers from a PxQ (e.g. 32×512, 16×128,32×1024, 64×1024) register file. While in one embodiment N may be up tothree sources and one destination register, alternative embodiments maysupport more or less sources and destination registers (e.g., maysupport up to two sources where one of these sources also acts as thedestination, may support up to three sources where one of these sourcesalso acts as the destination, may support up to two sources and onedestination).

Modifier field 2246—its content distinguishes occurrences ofinstructions in the generic vector instruction format that specifymemory access from those that do not; that is, between no memory access2205 instruction templates and memory access 2220 instruction templates.Memory access operations read and/or write to the memory hierarchy (insome cases specifying the source and/or destination addresses usingvalues in registers), while non-memory access operations do not (e.g.,the source and destinations are registers). While in one embodiment thisfield also selects between three different ways to perform memoryaddress calculations, alternative embodiments may support more, less, ordifferent ways to perform memory address calculations.

Augmentation operation field 2250—its content distinguishes which one ofa variety of different operations to be performed in addition to thebase operation. This field is context specific. In one embodiment of theinvention, this field is divided into a class field 2268, an alpha field2252, and a beta field 2254. The augmentation operation field 2250allows common groups of operations to be performed in a singleinstruction rather than 2, 3, or 4 instructions. Scale field 2260—itscontent allows for the scaling of the index field's content for memoryaddress generation (e.g., for address generation that uses2^(scale)*index+base).

Displacement Field 2262A—its content is used as part of memory addressgeneration (e.g., for address generation that uses2^(scale)*index+base+displacement). Displacement Factor Field 2262B(note that the juxtaposition of displacement field 2262A directly overdisplacement factor field 2262B indicates one or the other is used)—itscontent is used as part of address generation; it specifies adisplacement factor that is to be scaled by the size of a memory access(N)—where N is the number of bytes in the memory access (e.g., foraddress generation that uses 2^(scale)*index+base+scaled displacement).Redundant low-order bits are ignored and hence, the displacement factorfield's content is multiplied by the memory operands total size (N) inorder to generate the final displacement to be used in calculating aneffective address. The value of N is determined by the processorhardware at runtime based on the full opcode field 2274 (described laterherein) and the data manipulation field 2254C. The displacement field2262A and the displacement factor field 2262B are optional in the sensethat they are not used for the no memory access 2205 instructiontemplates and/or different embodiments may implement only one or none ofthe two.

Data element width field 2264—its content distinguishes which one of anumber of data element widths is to be used (in some embodiments for allinstructions; in other embodiments for only some of the instructions).This field is optional in the sense that it is not needed if only onedata element width is supported and/or data element widths are supportedusing some aspect of the opcodes.

Write mask field 2270—its content controls, on a per data elementposition basis, whether that data element position in the destinationvector operand reflects the result of the base operation andaugmentation operation. Class A instruction templates supportmerging-writemasking, while class B instruction templates support bothmerging- and zeroing-writemasking. When merging, vector masks allow anyset of elements in the destination to be protected from updates duringthe execution of any operation (specified by the base operation and theaugmentation operation); in other one embodiment, preserving the oldvalue of each element of the destination where the corresponding maskbit has a 0. In contrast, when zeroing vector masks allow any set ofelements in the destination to be zeroed during the execution of anyoperation (specified by the base operation and the augmentationoperation); in one embodiment, an element of the destination is set to 0when the corresponding mask bit has a 0 value. A subset of thisfunctionality is the ability to control the vector length of theoperation being performed (that is, the span of elements being modified,from the first to the last one); however, it is not necessary that theelements that are modified be consecutive. Thus, the write mask field2270 allows for partial vector operations, including loads, stores,arithmetic, logical, etc. While embodiments of the invention aredescribed in which the write mask field's 2270 content selects one of anumber of write mask registers that contains the write mask to be used(and thus the write mask field's 2270 content indirectly identifies thatmasking to be performed), alternative embodiments instead or additionalallow the mask write field's 2270 content to directly specify themasking to be performed.

Immediate field 2272—its content allows for the specification of animmediate. This field is optional in the sense that is it not present inan implementation of the generic vector friendly format that does notsupport immediate and it is not present in instructions that do not usean immediate. Class field 2268—its content distinguishes betweendifferent classes of instructions. With reference to FIG. 8A and FIG.8B, the contents of this field select between class A and class Binstructions. In FIG. 8A and FIG. 8B, rounded corner squares are used toindicate a specific value is present in a field (e.g., class A 2268A andclass B 2268B for the class field 2268 respectively in FIG. 8A and FIG.8B).

In the case of the non-memory access 2205 instruction templates of classA, the alpha field 2252 is interpreted as an RS field 2252A, whosecontent distinguishes which one of the different augmentation operationtypes are to be performed (e.g., round 2252A.1 and data transform2252A.2 are respectively specified for the no memory access, round typeoperation 2210 and the no memory access, data transform type operation2215 instruction templates), while the beta field 2254 distinguisheswhich of the operations of the specified type is to be performed. In theno memory access 2205 instruction templates, the scale field 2260, thedisplacement field 2262A, and the displacement scale filed 2262B are notpresent.

In the no memory access full round control type operation 2210instruction template, the beta field 2254 is interpreted as a roundcontrol field 2254A, whose content(s) provide static rounding. While inthe described embodiments of the invention the round control field 2254Aincludes a suppress all floating point exceptions (SAE) field 2256 and around operation control field 2258, alternative embodiments may supportmay encode both these concepts into the same field or only have one orthe other of these concepts/fields (e.g., may have only the roundoperation control field 2258).

SAE field 2256—its content distinguishes whether or not to disable theexception event reporting; when the SAE field's 2256 content indicatessuppression is enabled, a given instruction does not report any kind offloating-point exception flag and does not raise any floating pointexception handler.

Round operation control field 2258—its content distinguishes which oneof a group of rounding operations to perform (e.g., Round-up,Round-down, Round-towards-zero and Round-to-nearest). Thus, the roundoperation control field 2258 allows for the changing of the roundingmode on a per instruction basis. In one embodiment of the inventionwhere a processor includes a control register for specifying roundingmodes, the round operation control field's 2250 content overrides thatregister value.

In the no memory access data transform type operation 2215 instructiontemplate, the beta field 2254 is interpreted as a data transform field2254B, whose content distinguishes which one of a number of datatransforms is to be performed (e.g., no data transform, swizzle,broadcast).

In the case of a memory access 2220 instruction template of class A, thealpha field 2252 is interpreted as an eviction hint field 2252B, whosecontent distinguishes which one of the eviction hints is to be used (inFIG. 8A, temporal 2252B.1 and non-temporal 2252B.2 are respectivelyspecified for the memory access, temporal 2225 instruction template andthe memory access, non-temporal 2230 instruction template), while thebeta field 2254 is interpreted as a data manipulation field 2254C, whosecontent distinguishes which one of a number of data manipulationoperations (also known as primitives) is to be performed (e.g., nomanipulation; broadcast; up conversion of a source; and down conversionof a destination). The memory access 2220 instruction templates includethe scale field 2260, and optionally the displacement field 2262A or thedisplacement scale field 2262B.

Vector memory instructions perform vector loads from and vector storesto memory, with conversion support. As with regular vector instructions,vector memory instructions transfer data from/to memory in a dataelement-wise fashion, with the elements that are actually transferred isdictated by the contents of the vector mask that is selected as thewrite mask.

Temporal data is data likely to be reused soon enough to benefit fromcaching. This is, however, a hint, and different processors mayimplement it in different ways, including ignoring the hint entirely.Non-temporal data is data unlikely to be reused soon enough to benefitfrom caching in the 1st-level cache and should be given priority foreviction. This is, however, a hint, and different processors mayimplement it in different ways, including ignoring the hint entirely.

In the case of the instruction templates of class B, the alpha field2252 is interpreted as a write mask control (Z) field 2252C, whosecontent distinguishes whether the write masking controlled by the writemask field 2270 should be a merging or a zeroing.

In the case of the non-memory access 2205 instruction templates of classB, part of the beta field 2254 is interpreted as an RL field 2257A,whose content distinguishes which one of the different augmentationoperation types are to be performed (e.g., round 2257A.1 and vectorlength (VSIZE) 2257A.2 are respectively specified for the no memoryaccess, write mask control, partial round control type operation 2212instruction template and the no memory access, write mask control, VSIZEtype operation 2217 instruction template), while the rest of the betafield 2254 distinguishes which of the operations of the specified typeis to be performed. In the no memory access 2205 instruction templates,the scale field 2260, the displacement field 2262A, and the displacementscale filed 2262B are not present.

In the no memory access, write mask control, partial round control typeoperation 2210 instruction template, the rest of the beta field 2254 isinterpreted as a round operation field 2259A and exception eventreporting is disabled (a given instruction does not report any kind offloating-point exception flag and does not raise any floating pointexception handler).

Round operation control field 2259A—just as round operation controlfield 2258, its content distinguishes which one of a group of roundingoperations to perform (e.g., Round-up, Round-down, Round-towards-zeroand Round-to-nearest). Thus, the round operation control field 2259Aallows for the changing of the rounding mode on a per instruction basis.In one embodiment of the invention where a processor includes a controlregister for specifying rounding modes, the round operation controlfield's 2250 content overrides that register value.

In the no memory access, write mask control, VSIZE type operation 2217instruction template, the rest of the beta field 2254 is interpreted asa vector length field 2259B, whose content distinguishes which one of anumber of data vector lengths is to be performed on (e.g., 128, 256, or512 byte).

In the case of a memory access 2220 instruction template of class B,part of the beta field 2254 is interpreted as a broadcast field 2257B,whose content distinguishes whether or not the broadcast type datamanipulation operation is to be performed, while the rest of the betafield 2254 is interpreted the vector length field 2259B. The memoryaccess 2220 instruction templates include the scale field 2260, andoptionally the displacement field 2262A or the displacement scale field2262B.

With regard to the generic vector friendly instruction format 2200, afull opcode field 2274 is shown including the format field 2240, thebase operation field 2242, and the data element width field 2264. Whileone embodiment is shown where the full opcode field 2274 includes all ofthese fields, the full opcode field 2274 includes less than all of thesefields in embodiments that do not support all of them. The full opcodefield 2274 provides the operation code (opcode).

The augmentation operation field 2250, the data element width field2264, and the write mask field 2270 allow these features to be specifiedon a per instruction basis in the generic vector friendly instructionformat. The combination of write mask field and data element width fieldcreate typed instructions in that they allow the mask to be appliedbased on different data element widths.

The various instruction templates found within class A and class B arebeneficial in different situations. In some embodiments of theinvention, different processors or different cores within a processormay support only class A, only class B, or both classes. For instance, ahigh performance general purpose out-of-order core intended forgeneral-purpose computing may support only class B, a core intendedprimarily for graphics and/or scientific (throughput) computing maysupport only class A, and a core intended for both may support both (ofcourse, a core that has some mix of templates and instructions from bothclasses but not all templates and instructions from both classes iswithin the purview of the invention). Also, a single processor mayinclude multiple cores, all of which support the same class or in whichdifferent cores support different class. For instance, in a processorwith separate graphics and general purpose cores, one of the graphicscores intended primarily for graphics and/or scientific computing maysupport only class A, while one or more of the general purpose cores maybe high performance general purpose cores with out of order executionand register renaming intended for general-purpose computing thatsupport only class B. Another processor that does not have a separategraphics core, may include one more general purpose in-order orout-of-order cores that support both class A and class B. Of course,features from one class may also be implemented in the other class indifferent embodiments of the invention. Programs written in a high levellanguage would be put (e.g., just in time compiled or staticallycompiled) into an variety of different executable forms, including: 1) aform having only instructions of the class(es) supported by the targetprocessor for execution; or 2) a form having alternative routineswritten using different combinations of the instructions of all classesand having control flow code that selects the routines to execute basedon the instructions supported by the processor which is currentlyexecuting the code.

FIG. 9 is a block diagram illustrating an exemplary specific vectorfriendly instruction format according to embodiments of the invention.FIG. 9 shows a specific vector friendly instruction format 2300 that isspecific in the sense that it specifies the location, size,interpretation, and order of the fields, as well as values for some ofthose fields. The specific vector friendly instruction format 2300 maybe used to extend the x86 instruction set, and thus some of the fieldsare similar or the same as those used in the existing x86 instructionset and extension thereof (e.g., AVX). This format remains consistentwith the prefix encoding field, real opcode byte field, MOD R/M field,SIB field, displacement field, and immediate fields of the existing x86instruction set with extensions. The fields from FIG. 8 into which thefields from FIG. 9 map are illustrated.

It should be understood that, although embodiments of the invention aredescribed with reference to the specific vector friendly instructionformat 2300 in the context of the generic vector friendly instructionformat 2200 for illustrative purposes, the invention is not limited tothe specific vector friendly instruction format 2300 except whereclaimed. For example, the generic vector friendly instruction format2200 contemplates a variety of possible sizes for the various fields,while the specific vector friendly instruction format 2300 is shown ashaving fields of specific sizes. By way of specific example, while thedata element width field 2264 is illustrated as a one bit field in thespecific vector friendly instruction format 2300, the invention is notso limited (that is, the generic vector friendly instruction format 2200contemplates other sizes of the data element width field 2264).

The generic vector friendly instruction format 2200 includes thefollowing fields listed below in the order illustrated in FIG. 9A. EVEXPrefix (Bytes 0-3) 2302—is encoded in a four-byte form. Format Field2240 (EVEX Byte 0, bits [7:0])—the first byte (EVEX Byte 0) is theformat field 2240 and it contains 0x62 (the unique value used fordistinguishing the vector friendly instruction format in one embodimentof the invention). The second-fourth bytes (EVEX Bytes 1-3) include anumber of bit fields providing specific capability.

REX field 2305 (EVEX Byte 1, bits [7-5])—consists of a EVEX.R bit field(EVEX Byte 1, bit [7]-R), EVEX.X bit field (EVEX byte 1, bit [6]-X), and2257BEX byte 1, bit[5]-B). The EVEX.R, EVEX.X, and EVEX.B bit fieldsprovide the same functionality as the corresponding VEX bit fields, andare encoded using 1s complement form, i.e. ZMM0 is encoded as 1111B,ZMM15 is encoded as 0000B. Other fields of the instructions encode thelower three bits of the register indexes as is known in the art (rrr,xxx, and bbb), so that Rrrr, Xxxx, and Bbbb may be formed by addingEVEX.R, EVEX.X, and EVEX.B.

REX′ field 2210—this is the first part of the REX′ field 2210 and is theEVEX.R′ bit field (EVEX Byte 1, bit [4]-R′) that is used to encodeeither the upper 16 or lower 16 of the extended 32 register set. In oneembodiment of the invention, this bit, along with others as indicatedbelow, is stored in bit inverted format to distinguish (in thewell-known x86 32-bit mode) from the BOUND instruction, whose realopcode byte is 62, but does not accept in the MOD RIM field (describedbelow) the value of 11 in the MOD field; alternative embodiments of theinvention do not store this and the other indicated bits below in theinverted format. A value of 1 is used to encode the lower 16 registers.In other words, R′Rrrr is formed by combining EVEX.R′, EVEX.R, and theother RRR from other fields.

Opcode map field 2315 (EVEX byte 1, bits [3:0]-mmmm)—its content encodesan implied leading opcode byte (0F, 0F 38, or 0F 3). Data element widthfield 2264 (EVEX byte 2, bit [7]-W)—is represented by the notationEVEX.W. EVEX.W is used to define the granularity (size) of the datatype(either 32-bit data elements or 64-bit data elements). EVEX.vvvv 2320(EVEX Byte 2, bits [6:3]-vvvv)—the role of EVEX.vvvv may include thefollowing: 1) EVEX.vvvv encodes the first source register operand,specified in inverted (1s complement) form and is valid for instructionswith 2 or more source operands; 2) EVEX.vvvv encodes the destinationregister operand, specified in is complement form for certain vectorshifts; or 3) EVEX.vvvv does not encode any operand, the field isreserved and should contain 1111b. Thus, EVEX.vvvv field 2320 encodesthe 4 low-order bits of the first source register specifier stored ininverted (1s complement) form. Depending on the instruction, an extradifferent EVEX bit field is used to extend the specifier size to 32registers. EVEX.U 2268 Class field (EVEX byte 2, bit [2]-U)—If EVEX.U=0,it indicates class A or EVEX.U0; if EVEX.U=1, it indicates class B orEVEX.U1.

Prefix encoding field 2325 (EVEX byte 2, bits [1:0]-pp)—providesadditional bits for the base operation field. In addition to providingsupport for the legacy SSE instructions in the EVEX prefix format, thisalso has the benefit of compacting the SIMD prefix (rather thanrequiring a byte to express the SIMD prefix, the EVEX prefix requiresonly 2 bits). In one embodiment, to support legacy SSE instructions thatuse a SIMD prefix (66H, F2H, F3H) in both the legacy format and in theEVEX prefix format, these legacy SIMD prefixes are encoded into the SIMDprefix encoding field; and at runtime are expanded into the legacy SIMDprefix prior to being provided to the decoder's PLA (so the PLA canexecute both the legacy and EVEX format of these legacy instructionswithout modification). Although newer instructions could use the EVEXprefix encoding field's content directly as an opcode extension, certainembodiments expand in a similar fashion for consistency but allow fordifferent meanings to be specified by these legacy SIMD prefixes. Analternative embodiment may redesign the PLA to support the 2 bit SIMDprefix encodings, and thus not require the expansion.

Alpha field 2252 (EVEX byte 3, bit [7]-EH; also known as EVEX.EH,EVEX.rs, EVEX.RL, EVEX.write mask control, and EVEX.N; also illustratedwith a)—as previously described, this field is context specific. Betafield 2254 (EVEX byte 3, bits [6:4]-SSS, also known as EVEX.s₂₋₀,EVEX.r₂₋₀, EVEX.rr1, EVEX.LL0, EVEX.LLB; also illustrated with βββ)—aspreviously described, this field is context specific.

REX′ field 2210—this is the remainder of the REX′ field and is theEVEX.V′ bit field (EVEX Byte 3, bit [3]-V′) that may be used to encodeeither the upper 16 or lower 16 of the extended 32 register set. Thisbit is stored in bit inverted format. A value of 1 is used to encode thelower 16 registers. In other words, V′VVVV is formed by combiningEVEX.V′, EVEX.vvvv.

Write mask field 2270 (EVEX byte 3, bits [2:0]-kkk)—its contentspecifies the index of a register in the write mask registers aspreviously described. In one embodiment of the invention, the specificvalue EVEX kkk=000 has a special behavior implying no write mask is usedfor the particular instruction (this may be implemented in a variety ofways including the use of a write mask hardwired to all ones or hardwarethat bypasses the masking hardware).

Real Opcode Field 2330 (Byte 4) is also known as the opcode byte. Partof the opcode is specified in this field. MOD R/M Field 2340 (Byte 5)includes MOD field 2342, Reg field 2344, and R/M field 2346. Aspreviously described, the MOD field's 2342 content distinguishes betweenmemory access and non-memory access operations. The role of Reg field2344 can be summarized to two situations: encoding either thedestination register operand or a source register operand, or be treatedas an opcode extension and not used to encode any instruction operand.The role of R/M field 2346 may include the following: encoding theinstruction operand that references a memory address, or encoding eitherthe destination register operand or a source register operand.

Scale, Index, Base (SIB) Byte (Byte 6)—As previously described, thescale field's 2250 content is used for memory address generation.SIB.xxx 2354 and SIB.bbb 2356—the contents of these fields have beenpreviously referred to with regard to the register indexes Xxxx andBbbb. Displacement field 2262A (Bytes 7-10)—when MOD field 2342 contains10, bytes 7-10 are the displacement field 2262A, and it works the sameas the legacy 32-bit displacement (disp32) and works at bytegranularity.

Displacement factor field 2262B (Byte 7)—when MOD field 2342 contains01, byte 7 is the displacement factor field 2262B. The location of thisfield is that same as that of the legacy x86 instruction set 8-bitdisplacement (disp8), which works at byte granularity. Since disp8 issign extended, it can only address between −128 and 127 bytes offsets;in terms of 64 byte cache lines, disp8 uses 8 bits that can be set toonly four really useful values −128, −64, 0, and 64; since a greaterrange is often needed, disp32 is used; however, disp32 requires 4 bytes.In contrast to disp8 and disp32, the displacement factor field 2262B isa reinterpretation of disp8; when using displacement factor field 2262B,the actual displacement is determined by the content of the displacementfactor field multiplied by the size of the memory operand access (N).This type of displacement is referred to as disp8*N. This reduces theaverage instruction length (a single byte of used for the displacementbut with a much greater range). Such compressed displacement is based onthe assumption that the effective displacement is multiple of thegranularity of the memory access, and hence, the redundant low-orderbits of the address offset do not need to be encoded. In other words,the displacement factor field 2262B substitutes the legacy x86instruction set 8-bit displacement. Thus, the displacement factor field2262B is encoded the same way as an x86 instruction set 8-bitdisplacement (so no changes in the ModRM/SIB encoding rules) with theonly exception that disp8 is overloaded to disp8*N. In other words,there are no changes in the encoding rules or encoding lengths but onlyin the interpretation of the displacement value by hardware (which needsto scale the displacement by the size of the memory operand to obtain abyte-wise address offset). Immediate field 2272 operates as previouslydescribed.

FIG. 9B is a block diagram illustrating the fields of the specificvector friendly instruction format 2300 that make up the full opcodefield 2274 according to one embodiment of the invention. Specifically,the full opcode field 2274 includes the format field 2240, the baseoperation field 2242, and the data element width (W) field 2264. Thebase operation field 2242 includes the prefix encoding field 2325, theopcode map field 2315, and the real opcode field 2330.

FIG. 9C is a block diagram illustrating the fields of the specificvector friendly instruction format 2300 that make up the register indexfield 2244 according to one embodiment of the invention. Specifically,the register index field 2244 includes the REX field 2305, the REX′field 2310, the MODR/M.reg field 2344, the MODR/M.r/m field 2346, theVVVV field 2320, xxx field 2354, and the bbb field 2356.

FIG. 9D is a block diagram illustrating the fields of the specificvector friendly instruction format 2300 that make up the augmentationoperation field 2250 according to one embodiment of the invention. Whenthe class (U) field 2268 contains 0, it signifies EVEX.U0 (class A2268A); when it contains 1, it signifies EVEX.U1 (class B 2268B). WhenU=0 and the MOD field 2342 contains 11 (signifying a no memory accessoperation), the alpha field 2252 (EVEX byte 3, bit [7]-EH) isinterpreted as the rs field 2252A. When the rs field 2252A contains a 1(round 2252A.1), the beta field 2254 (EVEX byte 3, bits [6:4]-SSS) isinterpreted as the round control field 2254A. The round control field2254A includes a one bit SAE field 2256 and a two bit round operationfield 2258. When the rs field 2252A contains a 0 (data transform2252A.2), the beta field 2254 (EVEX byte 3, bits [6:4]-SSS) isinterpreted as a three bit data transform field 2254B. When U=0 and theMOD field 2342 contains 00, 01, or 10 (signifying a memory accessoperation), the alpha field 2252 (EVEX byte 3, bit [7]-EH) isinterpreted as the eviction hint (EH) field 2252B and the beta field2254 (EVEX byte 3, bits [6:4]-SSS) is interpreted as a three bit datamanipulation field 2254C.

When U=1, the alpha field 2252 (EVEX byte 3, bit [7]-EH) is interpretedas the write mask control (Z) field 2252C. When U=1 and the MOD field2342 contains 11 (signifying a no memory access operation), part of thebeta field 2254 (EVEX byte 3, bit [4]-S_(o)) is interpreted as the RLfield 2257A; when it contains a 1 (round 2257A.1) the rest of the betafield 2254 (EVEX byte 3, bit [6-5]-S₂₋₁) is interpreted as the roundoperation field 2259A, while when the RL field 2257A contains a 0 (VSIZE2257.A2) the rest of the beta field 2254 (EVEX byte 3, bit [6-5]-S₂₋₁)is interpreted as the vector length field 2259B (EVEX byte 3, bit[6-5]-L₁₋₀). When U=1 and the MOD field 2342 contains 00, 01, or 10(signifying a memory access operation), the beta field 2254 (EVEX byte3, bits [6:4]-SSS) is interpreted as the vector length field 2259B (EVEXbyte 3, bit [6-5]-L₁₋₀) and the broadcast field 2257B (EVEX byte 3, bit[4]-B).

FIG. 10 is a block diagram of a register architecture 2400 according toone embodiment of the invention. In the embodiment illustrated, thereare 32 vector registers 2410 that are 512 bits wide; these registers arereferenced as zmm0 through zmm31. The lower order 256 bits of the lower16 zmm registers are overlaid on registers ymm0-16. The lower order 128bits of the lower 16 zmm registers (the lower order 128 bits of the ymmregisters) are overlaid on registers xmm0-15. The specific vectorfriendly instruction format 2300 operates on these overlaid registerfile as illustrated in the below tables.

Adjustable Vector Length Class Operations Registers Instruction A(Figure 8A; 2210, 2215, zmm registers Templates that U = 0) 2225, 2230(the vector do not include length is 64 byte)

the vector length B (Figure 8B; 2212 zmm registers field 2259B U = 1)(the vector length is 64 byte) Instruction B (Figure 8B; 2217, 2227 zmm,ymm, or Templates that U = 1) xmm registers do include the (the vectorvector length length is 64 byte, field 2259B 32 byte, or 16 byte)depending on the vector length field 2259B

In other words, the vector length field 2259B selects between a maximumlength and one or more other shorter lengths, where each such shorterlength is half the length of the preceding length; and instructionstemplates without the vector length field 2259B operate on the maximumvector length. Further, in one embodiment, the class B instructiontemplates of the specific vector friendly instruction format 2300operate on packed or scalar single/double-precision floating point dataand packed or scalar integer data. Scalar operations are operationsperformed on the lowest order data element position in an zmm/ymm/xmmregister; the higher order data element positions are either left thesame as they were prior to the instruction or zeroed depending on theembodiment.

Write mask registers 2415—in the embodiment illustrated, there are 8write mask registers (k0 through k7), each 64 bits in size. In analternate embodiment, the write mask registers 2415 are 16 bits in size.As previously described, in one embodiment of the invention, the vectormask register k0 cannot be used as a write mask; when the encoding thatwould normally indicate k0 is used for a write mask, it selects ahardwired write mask of 0xFFFF, effectively disabling write masking forthat instruction.

General-purpose registers 2425—in the embodiment illustrated, there aresixteen 64-bit general-purpose registers that are used along with theexisting x86 addressing modes to address memory operands. Theseregisters are referenced by the names RAX, RBX, RCX, RDX, RBP, RSI, RDI,RSP, and R8 through R15.

Scalar floating point stack register file (x87 stack) 2445, on which isaliased the MMX packed integer flat register file 2450—in the embodimentillustrated, the x87 stack is an eight-element stack used to performscalar floating-point operations on 32/64/80-bit floating point datausing the x87 instruction set extension; while the MMX registers areused to perform operations on 64-bit packed integer data, as well as tohold operands for some operations performed between the MMX and XMMregisters.

Alternative embodiments of the invention may use wider or narrowerregisters. Additionally, alternative embodiments of the invention mayuse more, less, or different register files and registers.

Processor cores may be implemented in different ways, for differentpurposes, and in different processors. For instance, implementations ofsuch cores may include: 1) a general purpose in-order core intended forgeneral-purpose computing; 2) a high performance general purposeout-of-order core intended for general-purpose computing; 3) a specialpurpose core intended primarily for graphics and/or scientific(throughput) computing. Implementations of different processors mayinclude: 1) a CPU including one or more general purpose in-order coresintended for general-purpose computing and/or one or more generalpurpose out-of-order cores intended for general-purpose computing; and2) a coprocessor including one or more special purpose cores intendedprimarily for graphics and/or scientific (throughput). Such differentprocessors lead to different computer system architectures, which mayinclude: 1) the coprocessor on a separate chip from the CPU; 2) thecoprocessor on a separate die in the same package as a CPU; 3) thecoprocessor on the same die as a CPU (in which case, such a coprocessoris sometimes referred to as special purpose logic, such as integratedgraphics and/or scientific (throughput) logic, or as special purposecores); and 4) a system on a chip that may include on the same die thedescribed CPU (sometimes referred to as the application core(s) orapplication processor(s)), the above described coprocessor, andadditional functionality. Exemplary core architectures are describednext, followed by descriptions of exemplary processors and computerarchitectures.

FIG. 11A is a block diagram illustrating both an exemplary in-orderpipeline and an exemplary register renaming, out-of-orderissue/execution pipeline according to embodiments of the invention. FIG.11B is a block diagram illustrating both an exemplary embodiment of anin-order architecture core and an exemplary register renaming,out-of-order issue/execution architecture core to be included in aprocessor according to embodiments of the invention. The solid linedboxes illustrate the in-order pipeline and in-order core, while theoptional addition of the dashed lined boxes illustrates the registerrenaming, out-of-order issue/execution pipeline and core. Given that thein-order aspect is a subset of the out-of-order aspect, the out-of-orderaspect will be described.

In FIG. 11A, a processor pipeline 2500 includes a fetch stage 2502, alength decode stage 2504, a decode stage 2506, an allocation stage 2508,a renaming stage 2510, a scheduling (also known as a dispatch or issue)stage 2512, a register read/memory read stage 2514, an execute stage2516, a write back/memory write stage 2518, an exception handling stage2522, and a commit stage 2524.

FIG. 11B shows processor core 2590 including a front end unit 2530coupled to an execution engine unit 2550, and both are coupled to amemory unit 2570. The core 2590 may be a reduced instruction setcomputing (RISC) core, a complex instruction set computing (CISC) core,a very long instruction word (VLIW) core, or a hybrid or alternativecore type. As yet another option, the core 2590 may be a special-purposecore, such as, for example, a network or communication core, compressionengine, coprocessor core, general purpose computing graphics processingunit (GPGPU) core, graphics core, or the like.

The front end unit 2530 includes a branch prediction unit 2532 coupledto an instruction cache unit 2534, which is coupled to an instructiontranslation lookaside buffer (TLB) 2536, which is coupled to aninstruction fetch unit 2538, which is coupled to a decode unit 2540. Thedecode unit 2540 (or decoder) may decode instructions, and generate asan output one or more micro-operations, micro-code entry points,microinstructions, other instructions, or other control signals, whichare decoded from, or which otherwise reflect, or are derived from, theoriginal instructions. The decode unit 2540 may be implemented usingvarious different mechanisms. Examples of suitable mechanisms include,but are not limited to, look-up tables, hardware implementations,programmable logic arrays (PLAs), microcode read only memories (ROMs),etc. In one embodiment, the core 2590 includes a microcode ROM or othermedium that stores microcode for certain macroinstructions (e.g., indecode unit 2540 or otherwise within the front end unit 2530). Thedecode unit 2540 is coupled to a rename/allocator unit 2552 in theexecution engine unit 2550.

The execution engine unit 2550 includes the rename/allocator unit 2552coupled to a retirement unit 2554 and a set of one or more schedulerunit(s) 2556. The scheduler unit(s) 2556 represents any number ofdifferent schedulers, including reservations stations, centralinstruction window, etc. The scheduler unit(s) 2556 is coupled to thephysical register file(s) unit(s) 2558. Each of the physical registerfile(s) units 2558 represents one or more physical register files,different ones of which store one or more different data types, such asscalar integer, scalar floating point, packed integer, packed floatingpoint, vector integer, vector floating point, status (e.g., aninstruction pointer that is the address of the next instruction to beexecuted), etc.

In one embodiment, the physical register file(s) unit 2558 comprises avector registers unit, a write mask registers unit, and a scalarregisters unit. These register units may provide architectural vectorregisters, vector mask registers, and general purpose registers. Thephysical register file(s) unit(s) 2558 is overlapped by the retirementunit 2554 to illustrate various ways in which register renaming andout-of-order execution may be implemented (e.g., using a reorderbuffer(s) and a retirement register file(s); using a future file(s), ahistory buffer(s), and a retirement register file(s); using a registermaps and a pool of registers; etc.). The retirement unit 2554 and thephysical register file(s) unit(s) 2558 are coupled to the executioncluster(s) 2560.

The execution cluster(s) 2560 includes a set of one or more executionunits 2562 and a set of one or more memory access units 2564. Theexecution units 2562 may perform various operations (e.g., shifts,addition, subtraction, multiplication) and on various types of data(e.g., scalar floating point, packed integer, packed floating point,vector integer, vector floating point). While some embodiments mayinclude a number of execution units dedicated to specific functions orsets of functions, other embodiments may include only one execution unitor multiple execution units that all perform all functions.

The scheduler unit(s) 2556, physical register file(s) unit(s) 2558, andexecution cluster(s) 2560 are shown as being possibly plural becausecertain embodiments create separate pipelines for certain types ofdata/operations (e.g., a scalar integer pipeline, a scalar floatingpoint/packed integer/packed floating point/vector integer/vectorfloating point pipeline, and/or a memory access pipeline that each havetheir own scheduler unit, physical register file(s) unit, and/orexecution cluster—and in the case of a separate memory access pipeline,certain embodiments are implemented in which only the execution clusterof this pipeline has the memory access unit(s) 2564). It should also beunderstood that where separate pipelines are used, one or more of thesepipelines may be out-of-order issue/execution and the rest in-order.

The set of memory access units 2564 is coupled to the memory unit 2570,which includes a data TLB unit 2572 coupled to a data cache unit 2574coupled to a level 2 (L2) cache unit 2576. In one exemplary embodiment,the memory access units 2564 may include a load unit, a store addressunit, and a store data unit, each of which is coupled to the data TLBunit 2572 in the memory unit 2570. The instruction cache unit 2534 isfurther coupled to a level 2 (L2) cache unit 2576 in the memory unit2570. The L2 cache unit 2576 is coupled to one or more other levels ofcache and eventually to a main memory.

By way of example, the exemplary register renaming, out-of-orderissue/execution core architecture may implement the pipeline 2500 asfollows: 1) the instruction fetch 2538 performs the fetch and lengthdecoding stages 2502 and 2504; 2) the decode unit 2540 performs thedecode stage 2506; 3) the rename/allocator unit 2552 performs theallocation stage 2508 and renaming stage 2510; 4) the scheduler unit(s)2556 performs the schedule stage 2512; 5) the physical register file(s)unit(s) 2558 and the memory unit 2570 perform the register read/memoryread stage 2514; the execution cluster 2560 perform the execute stage2516; 6) the memory unit 2570 and the physical register file(s) unit(s)2558 perform the write back/memory write stage 2518; 7) various unitsmay be involved in the exception handling stage 2522; and 8) theretirement unit 2554 and the physical register file(s) unit(s) 2558perform the commit stage 2524.

The core 2590 may support one or more instructions sets (e.g., the x86instruction set (with some extensions that have been added with newerversions); the MIPS instruction set of MIPS Technologies of Sunnyvale,Calif.; the ARM instruction set (with optional additional extensionssuch as NEON) of ARM Holdings of Sunnyvale, Calif.), including theinstruction(s) described herein. In one embodiment, the core 2590includes logic to support a packed data instruction set extension (e.g.,AVX1, AVX2, and/or some form of the generic vector friendly instructionformat (U=0 and/or U=1) previously described), thereby allowing theoperations used by many multimedia applications to be performed usingpacked data.

It should be understood that the core may support multithreading(executing two or more parallel sets of operations or threads), and maydo so in a variety of ways including time sliced multithreading,simultaneous multithreading (where a single physical core provides alogical core for each of the threads that physical core issimultaneously multithreading), or a combination thereof (e.g., timesliced fetching and decoding and simultaneous multithreading thereaftersuch as in the Intel® Hyperthreading technology).

While register renaming is described in the context of out-of-orderexecution, it should be understood that register renaming may be used inan in-order architecture. While the illustrated embodiment of theprocessor also includes separate instruction and data cache units2534/2574 and a shared L2 cache unit 2576, alternative embodiments mayhave a single internal cache for both instructions and data, such as,for example, a Level 1 (L1) internal cache, or multiple levels ofinternal cache. In some embodiments, the system may include acombination of an internal cache and an external cache that is externalto the core and/or the processor. Alternatively, all of the cache may beexternal to the core and/or the processor.

FIG. 12A and FIG. 12B illustrate a block diagram of a more specificexemplary in-order core architecture, which core would be one of severallogic blocks (including other cores of the same type and/or differenttypes) in a chip. The logic blocks communicate through a high-bandwidthinterconnect network (e.g., a ring network) with some fixed functionlogic, memory I/O interfaces, and other necessary I/O logic, dependingon the application.

FIG. 12A is a block diagram of a single processor core, along with itsconnection to the on-die interconnect network 2602 and with its localsubset of the Level 2 (L2) cache 2604, according to embodiments of theinvention. In one embodiment, an instruction decoder 2600 supports thex86 instruction set with a packed data instruction set extension. An L1cache 2606 allows low-latency accesses to cache memory into the scalarand vector units. While in one embodiment (to simplify the design), ascalar unit 2608 and a vector unit 2610 use separate register sets(respectively, scalar registers 2612 and vector registers 2614) and datatransferred between them is written to memory and then read back in froma level 1 (L1) cache 2606, alternative embodiments of the invention mayuse a different approach (e.g., use a single register set or include acommunication path that allow data to be transferred between the tworegister files without being written and read back).

The local subset of the L2 cache 2604 is part of a global L2 cache thatis divided into separate local subsets, one per processor core. Eachprocessor core has a direct access path to its own local subset of theL2 cache 2604. Data read by a processor core is stored in its L2 cachesubset 2604 and can be accessed quickly, in parallel with otherprocessor cores accessing their own local L2 cache subsets. Data writtenby a processor core is stored in its own L2 cache subset 2604 and isflushed from other subsets, if necessary. The ring network ensurescoherency for shared data. The ring network is bi-directional to allowagents such as processor cores, L2 caches and other logic blocks tocommunicate with each other within the chip. Each ring data-path is1012-bits wide per direction.

FIG. 12B is an expanded view of part of the processor core in FIG. 12Aaccording to embodiments of the invention. FIG. 12B includes an L1 datacache 2606A part of the L1 cache 2604, as well as more detail regardingthe vector unit 2610 and the vector registers 2614. Specifically, thevector unit 2610 is a 16-wide vector processing unit (VPU) (see the16-wide ALU 2628), which executes one or more of integer,single-precision float, and double-precision float instructions. The VPUsupports swizzling the register inputs with swizzle unit 2620, numericconversion with numeric convert units 2622A-B, and replication withreplication unit 2624 on the memory input. Write mask registers 2626allow predicating resulting vector writes.

FIG. 13 is a block diagram of a processor 2700 that may have more thanone core, may have an integrated memory controller, and may haveintegrated graphics according to embodiments of the invention. The solidlined boxes in FIG. 13 illustrate a processor 2700 with a single core2702A, a system agent 2710, a set of one or more bus controller units2716, while the optional addition of the dashed lined boxes illustratesan alternative processor 2700 with multiple cores 2702A-N, a set of oneor more integrated memory controller unit(s) 2714 in the system agentunit 2710, and special purpose logic 2708.

Thus, different implementations of the processor 2700 may include: 1) aCPU with the special purpose logic 2708 being integrated graphics and/orscientific (throughput) logic (which may include one or more cores), andthe cores 2702A-N being one or more general purpose cores (e.g., generalpurpose in-order cores, general purpose out-of-order cores, acombination of the two); 2) a coprocessor with the cores 2702A-N being alarge number of special purpose cores intended primarily for graphicsand/or scientific (throughput); and 3) a coprocessor with the cores2702A-N being a large number of general purpose in-order cores. Thus,the processor 2700 may be a general-purpose processor, coprocessor orspecial-purpose processor, such as, for example, a network orcommunication processor, compression engine, graphics processor, GPGPU(general purpose graphics processing unit), a high-throughput manyintegrated core (MIC) coprocessor (including 30 or more cores), embeddedprocessor, or the like. The processor may be implemented on one or morechips. The processor 2700 may be a part of and/or may be implemented onone or more substrates using any of a number of process technologies,such as, for example, BiCMOS, CMOS, or NMOS.

The memory hierarchy includes one or more levels of cache within thecores, a set or one or more shared cache units 2706, and external memory(not shown) coupled to the set of integrated memory controller units2714. The set of shared cache units 2706 may include one or moremid-level caches, such as level 2 (L2), level 3 (L3), level 4 (L4), orother levels of cache, a last level cache (LLC), and/or combinationsthereof. While in one embodiment a ring based interconnect unit 2712interconnects the integrated graphics logic 2708, the set of sharedcache units 2706, and the system agent unit 2710/integrated memorycontroller unit(s) 2714, alternative embodiments may use any number ofwell-known techniques for interconnecting such units. In one embodiment,coherency is maintained between one or more cache units 2706 and cores2702-A-N.

In some embodiments, one or more of the cores 2702A-N are capable ofmulti-threading. The system agent 2710 includes those componentscoordinating and operating cores 2702A-N. The system agent unit 2710 mayinclude for example a power control unit (PCU) and a display unit. ThePCU may be or include logic and components needed for regulating thepower state of the cores 2702A-N and the integrated graphics logic 2708.The display unit is for driving one or more externally connecteddisplays.

The cores 2702A-N may be homogenous or heterogeneous in terms ofarchitecture instruction set; that is, two or more of the cores 2702A-Nmay be capable of execution the same instruction set, while others maybe capable of executing only a subset of that instruction set or adifferent instruction set.

FIG. 14 to FIG. 18 are block diagrams of exemplary computerarchitectures. Other system designs and configurations known in the artsfor laptops, desktops, handheld PCs, personal digital assistants,engineering workstations, servers, network devices, network hubs,switches, embedded processors, digital signal processors (DSPs),graphics devices, video game devices, set-top boxes, micro controllers,cell phones, portable media players, hand held devices, and variousother electronic devices, are also suitable. In general, a huge varietyof systems or electronic devices capable of incorporating a processorand/or other execution logic as disclosed herein are generally suitable.

Referring now to FIG. 14, shown is a block diagram of a system 2800 inaccordance with one embodiment of the present invention. The system 2800may include one or more processors 2810, 2815, which are coupled to acontroller hub 2820. In one embodiment the controller hub 2820 includesa graphics memory controller hub (GMCH) 2890 and an Input/Output Hub(IOH) 2850 (which may be on separate chips); the GMCH 2890 includesmemory and graphics controllers to which are coupled memory 2840 and acoprocessor 2845; the IOH 2850 is couples input/output (I/O) devices2860 to the GMCH 2890. Alternatively, one or both of the memory andgraphics controllers are integrated within the processor (as describedherein), the memory 2840 and the coprocessor 2845 are coupled directlyto the processor 2810, and the controller hub 2820 in a single chip withthe IOH 2850.

The optional nature of additional processors 2815 is denoted in FIG. 14with broken lines. Each processor 2810, 2815 may include one or more ofthe processing cores described herein and may be some version of theprocessor 2700.

The memory 2840 may be, for example, dynamic random access memory(DRAM), phase change memory (PCM), or a combination of the two. For atleast one embodiment, the controller hub 2820 communicates with theprocessor(s) 2810, 2815 via a multi-drop bus, such as a frontside bus(FSB), point-to-point interface such as QuickPath Interconnect (QPI), orsimilar connection 2895.

In one embodiment, the coprocessor 2845 is a special-purpose processor,such as, for example, a high-throughput MIC processor, a network orcommunication processor, compression engine, graphics processor, GPGPU,embedded processor, or the like. In one embodiment, controller hub 2820may include an integrated graphics accelerator.

There can be a variety of differences between the physical resources2810, 2815 in terms of a spectrum of metrics of merit includingarchitectural, microarchitectural, thermal, power consumptioncharacteristics, and the like.

In one embodiment, the processor 2810 executes instructions that controldata processing operations of a general type. Embedded within theinstructions may be coprocessor instructions. The processor 2810recognizes these coprocessor instructions as being of a type that shouldbe executed by the attached coprocessor 2845. Accordingly, the processor2810 issues these coprocessor instructions (or control signalsrepresenting coprocessor instructions) on a coprocessor bus or otherinterconnect, to coprocessor 2845. Coprocessor(s) 2845 accept andexecute the received coprocessor instructions.

Referring now to FIG. 15, shown is a block diagram of a first morespecific exemplary system 2900 in accordance with an embodiment of thepresent invention. As shown in FIG. 15, multiprocessor system 2900 is apoint-to-point interconnect system, and includes a first processor 2970and a second processor 2980 coupled via a point-to-point interconnect2950. Each of processors 2970 and 2980 may be some version of theprocessor 2700. In one embodiment of the invention, processors 2970 and2980 are respectively processors 2810 and 2815, while coprocessor 2938is coprocessor 2845. In another embodiment, processors 2970 and 2980 arerespectively processor 2810 coprocessor 2845.

Processors 2970 and 2980 are shown including integrated memorycontroller (IMC) units 2972 and 2982, respectively. Processor 2970 alsoincludes as part of its bus controller units point-to-point (P-P)interfaces 2976 and 2978; similarly, second processor 2980 includes P-Pinterfaces 2986 and 2988. Processors 2970, 2980 may exchange informationvia a point-to-point (P-P) interface 2950 using P-P interface circuits2978, 2988. As shown in FIG. 15, IMCs 2972 and 2982 couple theprocessors to respective memories, namely a memory 2932 and a memory2934, which may be portions of main memory locally attached to therespective processors.

Processors 2970, 2980 may each exchange information with a chipset 2990via individual P-P interfaces 2952, 2954 using point to point interfacecircuits 2976, 2994, 2986, 2998. Chipset 2990 may optionally exchangeinformation with the coprocessor 2938 via a high-performance interface2939. In one embodiment, the coprocessor 2938 is a special-purposeprocessor, such as, for example, a high-throughput MIC processor, anetwork or communication processor, compression engine, graphicsprocessor, GPGPU, embedded processor, or the like.

A shared cache (not shown) may be included in either processor oroutside of both processors, yet connected with the processors via P-Pinterconnect, such that either or both processors' local cacheinformation may be stored in the shared cache if a processor is placedinto a low power mode. Chipset 2990 may be coupled to a first bus 2916via an interface 2996. In one embodiment, first bus 2916 may be aPeripheral Component Interconnect (PCI) bus, or a bus such as a PCIExpress bus or another third generation I/O interconnect bus, althoughthe scope of the present invention is not so limited.

As shown in FIG. 15, various I/O devices 2914 may be coupled to firstbus 2916, along with a bus bridge 2918 which couples first bus 2916 to asecond bus 2920. In one embodiment, one or more additional processor(s)2915, such as coprocessors, high-throughput MIC processors, GPGPU's,accelerators (such as, e.g., graphics accelerators or digital signalprocessing (DSP) units), field programmable gate arrays, or any otherprocessor, are coupled to first bus 2916. In one embodiment, second bus2920 may be a low pin count (LPC) bus. Various devices may be coupled toa second bus 2920 including, for example, a keyboard and/or mouse 2922,communication devices 2927 and a storage unit 2928 such as a disk driveor other mass storage device which may include instructions/code anddata 2930, in one embodiment. Further, an audio I/O 2924 may be coupledto the second bus 2920. Note that other architectures are possible. Forexample, instead of the point-to-point architecture of FIG. 15, a systemmay implement a multi-drop bus or other such architecture.

Referring now to FIG. 16, shown is a block diagram of a second morespecific exemplary system 3000 in accordance with an embodiment of thepresent invention. Like elements in FIG. 16 and FIG. 17 bear likereference numerals, and certain aspects of FIG. 15 have been omittedfrom FIG. 16 in order to avoid obscuring other aspects of FIG. 16.

FIG. 16 illustrates that the processors 2970, 2980 may includeintegrated memory and I/O control logic (“CL”) 2972 and 2982,respectively. Thus, the CL 2972, 2982 include integrated memorycontroller units and include I/O control logic. FIG. 16 illustrates thatnot only are the memories 2932, 2934 coupled to the CL 2972, 2982, butalso that I/O devices 3014 are also coupled to the control logic 2972,2982. Legacy I/O devices 3015 are coupled to the chipset 2990.

Referring now to FIG. 17, shown is a block diagram of a SoC 3100 inaccordance with an embodiment of the present invention. Similar elementsin FIG. 13 bear like reference numerals. Also, dashed lined boxes areoptional features on more advanced SoCs. In FIG. 17, an interconnectunit(s) 3102 is coupled to: an application processor 3110 which includesa set of one or more cores 202A-N and shared cache unit(s) 2706; asystem agent unit 2710; a bus controller unit(s) 2716; an integratedmemory controller unit(s) 2714; a set or one or more coprocessors 3120which may include integrated graphics logic, an image processor, anaudio processor, and a video processor; an static random access memory(SRAM) unit 3130; a direct memory access (DMA) unit 3132; and a displayunit 3140 for coupling to one or more external displays. In oneembodiment, the coprocessor(s) 3120 include a special-purpose processor,such as, for example, a network or communication processor, compressionengine, GPGPU, a high-throughput MIC processor, embedded processor, orthe like.

Embodiments of the mechanisms disclosed herein may be implemented inhardware, software, firmware, or a combination of such implementationapproaches. Embodiments of the invention may be implemented as computerprograms or program code executing on programmable systems comprising atleast one processor, a storage system (including volatile andnon-volatile memory and/or storage elements), at least one input device,and at least one output device.

Program code, such as code 2930 illustrated in FIG. 15, may be appliedto input instructions to perform the functions described herein andgenerate output information. The output information may be applied toone or more output devices, in known fashion. For purposes of thisapplication, a processing system includes any system that has aprocessor, such as, for example; a digital signal processor (DSP), amicrocontroller, an application specific integrated circuit (ASIC), or amicroprocessor.

The program code may be implemented in a high level procedural or objectoriented programming language to communicate with a processing system.The program code may also be implemented in assembly or machinelanguage, if desired. In fact, the mechanisms described herein are notlimited in scope to any particular programming language. In any case,the language may be a compiled or interpreted language.

One or more aspects of at least one embodiment may be implemented byrepresentative instructions stored on a machine-readable medium whichrepresents various logic within the processor, which when read by amachine causes the machine to fabricate logic to perform the techniquesdescribed herein. Such representations, known as “IP cores” may bestored on a tangible, machine readable medium and supplied to variouscustomers or manufacturing facilities to load into the fabricationmachines that actually make the logic or processor.

Such machine-readable storage media may include, without limitation,non-transitory, tangible arrangements of articles manufactured or formedby a machine or device, including storage media such as hard disks, anyother type of disk including floppy disks, optical disks, compact diskread-only memories (CD-ROMs), compact disk rewritable's (CD-RWs), andmagneto-optical disks, semiconductor devices such as read-only memories(ROMs), random access memories (RAMs) such as dynamic random accessmemories (DRAMs), static random access memories (SRAMs), erasableprogrammable read-only memories (EPROMs), flash memories, electricallyerasable programmable read-only memories (EEPROMs), phase change memory(PCM), magnetic or optical cards, or any other type of media suitablefor storing electronic instructions.

Accordingly, embodiments of the invention also include non-transitory,tangible machine-readable media containing instructions or containingdesign data, such as Hardware Description Language (HDL), which definesstructures, circuits, apparatuses, processors and/or system featuresdescribed herein. Such embodiments may also be referred to as programproducts.

In some cases, an instruction converter may be used to convert aninstruction from a source instruction set to a target instruction set.For example, the instruction converter may translate (e.g., using staticbinary translation, dynamic binary translation including dynamiccompilation), morph, emulate, or otherwise convert an instruction to oneor more other instructions to be processed by the core. The instructionconverter may be implemented in software, hardware, firmware, or acombination thereof. The instruction converter may be on processor, offprocessor, or part on and part off processor.

FIG. 18 is a block diagram contrasting the use of a software instructionconverter to convert binary instructions in a source instruction set tobinary instructions in a target instruction set according to embodimentsof the invention. In the illustrated embodiment, the instructionconverter is a software instruction converter, although alternativelythe instruction converter may be implemented in software, firmware,hardware, or various combinations thereof. FIG. 18 shows a program in ahigh level language 3202 may be compiled using an x86 compiler 3204 togenerate x86 binary code 3206 that may be natively executed by aprocessor with at least one x86 instruction set core 3216. The processorwith at least one x86 instruction set core 3216 represents any processorthat can perform substantially the same functions as an Intel processorwith at least one x86 instruction set core by compatibly executing orotherwise processing (1) a substantial portion of the instruction set ofthe Intel x86 instruction set core or (2) object code versions ofapplications or other software targeted to run on an Intel processorwith at least one x86 instruction set core, in order to achievesubstantially the same result as an Intel processor with at least onex86 instruction set core. The x86 compiler 3204 represents a compilerthat is operable to generate x86 binary code 3206 (e.g., object code)that can, with or without additional linkage processing, be executed onthe processor with at least one x86 instruction set core 3216.Similarly, FIG. 18 shows the program in the high level language 3202 maybe compiled using an alternative instruction set compiler 3208 togenerate alternative instruction set binary code 3210 that may benatively executed by a processor without at least one x86 instructionset core 3214 (e.g., a processor with cores that execute the MIPSinstruction set of MIPS Technologies of Sunnyvale, Calif. and/or thatexecute the ARM instruction set of ARM Holdings of Sunnyvale, Calif.).The instruction converter 3212 is used to convert the x86 binary code3206 into code that may be natively executed by the processor without anx86 instruction set core 3214. This converted code is not likely to bethe same as the alternative instruction set binary code 3210 because aninstruction converter capable of this is difficult to make; however, theconverted code will accomplish the general operation and be made up ofinstructions from the alternative instruction set. Thus, the instructionconverter 3212 represents software, firmware, hardware, or a combinationthereof that, through emulation, simulation or any other process, allowsa processor or other electronic device that does not have an x86instruction set processor or core to execute the x86 binary code 3206.

Some portions of the preceding detailed descriptions have been presentedin terms of algorithms and symbolic representations of operations ondata bits within a computer memory. These algorithmic descriptions andrepresentations are the ways used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. An algorithm is here, and generally,conceived to be a self-consistent sequence of operations leading to adesired result. The operations are those requiring physicalmanipulations of physical quantities.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the above discussion, itis appreciated that throughout the description, discussions utilizingterms such as those set forth in the claims below, refer to the actionand processes of a computer system, or similar electronic computingdevice, that manipulates and transforms data represented as physical(electronic) quantities within the computer system's registers andmemories into other data similarly represented as physical quantitieswithin the computer system memories or registers or other suchinformation storage, transmission or display devices.

The techniques shown in the figures can be implemented using code anddata stored and executed on one or more electronic devices. Suchelectronic devices store and communicate (internally and/or with otherelectronic devices over a network) code and data using computer-readablemedia, such as non-transitory computer-readable storage media (e.g.,magnetic disks; optical disks; random access memory; read only memory;flash memory devices; phase-change memory) and transitorycomputer-readable transmission media (e.g., electrical, optical,acoustical or other form of propagated signals—such as carrier waves,infrared signals, digital signals).

The processes or methods depicted in the preceding figures may beperformed by processing logic that comprises hardware (e.g. circuitry,dedicated logic, etc.), firmware, software (e.g., embodied on anon-transitory computer readable medium), or a combination of both.Although the processes or methods are described above in terms of somesequential operations, it should be appreciated that some of theoperations described may be performed in a different order. Moreover,some operations may be performed in parallel rather than sequentially.

In the foregoing specification, embodiments of the invention have beendescribed with reference to specific exemplary embodiments thereof. Itwill be evident that various modifications may be made thereto withoutdeparting from the broader spirit and scope of the invention as setforth in the following claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense.

What is claimed is:
 1. A processor, comprising: an instruction decoderto receive an instruction to process a multiply-accumulate operation,the instruction having a first operand, a second operand, a thirdoperand, and a fourth operand, first operand to specify a first storagelocation to store an accumulated value, the second operand to specify asecond storage location to store a first value and a second value, thethird operand to specify a third storage location to store a thirdvalue; and an execution unit coupled to the instruction decoder toperform the multiply-accumulate operation to multiply the first valuewith the second value to generate a multiply result and to accumulatethe multiply result and at least a portion of a third value to theaccumulated value based on the fourth operand.
 2. The processor of claim1, wherein a result of the multiply-accumulate operation is stored inthe first storage location indicated by the first operand.
 3. Theprocessor of claim 1, wherein the fourth operand specifies a fourthstorage location to store a value indicating the at least a portion ofthe third value to be added to the accumulated value.
 4. The processorof claim 3, wherein a higher portion of the third value is accumulatedwhen the value of the fourth storage location contains a first value,and wherein a lower portion of the third value is accumulated when thevalue of the fourth storage location contains a second value.
 5. Theprocessor of claim 1, wherein the first, second, and third operands haveat least 512 bits, and wherein the execution unit is to perform at leastfour iterations of the multiply-accumulate operation, each iterationoccupying at least 128 bits.
 6. The processor of claim 1, wherein for acurrent iteration of multiply-accumulate operations, a multiplication isperformed between the (i+63:i) bits of the second operand and the(i+127:i+64) bits of the second operand, a first addition is performedbetween the multiplication and the (i+63:i) bits of the first operand,and a second addition is performed between the first addition and the(i+63:i) bits of the third operand as specified by the fourth operand.7. The processor of claim 6, wherein a third addition is performedbetween a first set of carry bits resulting from the first addition anda second set of carry bits resulting from the second addition.
 8. Theprocessor of claim 6, wherein the second addition is performed betweenthe first addition and the (i+127:i+64) bits of the third operand asspecified by the fourth operand.
 9. A method, comprising: receiving, byan instruction decoder of a processor, an instruction having a firstoperand, a second operand, a third operand, and fourth operand, firstoperand to specify a first storage location to store an accumulatedvalue, the second operand to specify a second storage location to storea first value and a second value, the third operand to specify a thirdstorage location to store a third value; and performing, by an executionunit of the processor, a multiply-accumulate operation to multiply thefirst value with the second value to generate a multiply result and toaccumulate the multiply result and at least a portion of a third valueto an accumulated value based on the fourth operand.
 10. The method ofclaim 9, wherein a result of the multiply-accumulate operation is storedin the first storage location indicated by the first operand.
 11. Themethod of claim 9, wherein the fourth operand specifies a fourth storagelocation to store a value indicating the at least a portion of the thirdvalue to be added to the accumulated value.
 12. The method of claim 11,wherein a higher portion of the third value is accumulated when thevalue of the fourth storage location contains a first value, and whereina lower portion of the third value is accumulated when the value of thefourth storage location contains a second value.
 13. The method of claim9, wherein the first, second, and third operands have at least 512 bits,and wherein the execution unit is to perform at least four iterations ofthe multiply-accumulate operation, each iteration occupying at least 128bits.
 14. The method of claim 9, wherein for a current iteration ofmultiply-accumulate operations, a multiplication is performed betweenthe (i+63:i) bits of the second operand and the (i+127:i+64) bits of thesecond operand, a first addition is performed between the multiplicationand the (i+63:i) bits of the first operand, and a second addition isperformed between the first addition and the (i+63:i) bits of the thirdoperand as specified by the fourth operand.
 15. The method of claim 14,wherein a third addition is performed between a first set of carry bitsresulting from the first addition and a second set of carry bitsresulting from the second addition.
 16. The method of claim 14, whereinthe second addition is performed between the first addition and the(i+127:i+64) bits of the third operand as specified by the fourthoperand.
 17. A data processing system, comprising: an interconnect; aprocessor coupled to the interconnect to receive an instruction having afirst operand, a second operand, a third operand, and fourth operand,first operand to specify a first storage location to store anaccumulated value, the second operand to specify a second storagelocation to store a first value and a second value, the third operand tospecify a third storage location to store a third value, and theprocessor to perform a multiply-accumulate operation to multiply thefirst value with the second value to generate a multiply result and toaccumulate the multiply result and at least a portion of a third valueto an accumulated value based on the fourth operand; and a dynamicrandom access (DRAM) coupled to the interconnect.
 18. The system ofclaim 17, wherein a result of the multiply-accumulate operation isstored in the first storage location indicated by the first operand. 19.The system of claim 17, wherein the fourth operand specifies a fourthstorage location to store a value indicating the at least a portion ofthe third value to be added to the accumulated value.
 20. The system ofclaim 19, wherein a higher portion of the third value is accumulatedwhen the value of the fourth storage location contains a first value,and wherein a lower portion of the third value is accumulated when thevalue of the fourth storage location contains a second value.
 21. Thesystem of claim 17, wherein the first, second, and third operands haveat least 512 bits, and wherein the execution unit is to perform at leastfour iterations of the multiply-accumulate operation, each iterationoccupying at least 128 bits.
 22. The system of claim 17, wherein for acurrent iteration of multiply-accumulate operations, a multiplication isperformed between the (i+63:i) bits of the second operand and the(i+127:i+64) bits of the second operand, a first addition is performedbetween the multiplication and the (i+63:i) bits of the first operand,and a second addition is performed between the first addition and the(i+63:i) bits of the third operand as specified by the fourth operand.23. The system of claim 22, wherein a third addition is performedbetween a first set of carry bits resulting from the first addition anda second set of carry bits resulting from the second addition.
 24. Thesystem of claim 22, wherein the second addition is performed between thefirst addition and the (i+127:i+64) bits of the third operand asspecified by the fourth operand.